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In-Use Encryption

Encryption Keys and Key Vaults

On this page

  • Overview
  • Data Encryption Keys and the Customer Master Key
  • Key Rotation
  • Key Vault Collections
  • Key Vault collection Name
  • Permissions
  • Key Vault Cluster
  • Update a Key Vault Collection

Overview

In this guide, you can learn details about the following components of In-Use Encryption:

  • Data Encryption Keys (DEK)s

  • Customer Master Keys (CMK)s

  • Key Vault collections

  • Key Management System (KMS)

To view step by step guides demonstrating how to use the preceding components to set up a Queryable Encryption or Client-Side Field Level Encryption enabled client, see the following resources:

Data Encryption Keys and the Customer Master Key

In-use encryption uses a multi-level key hierarchy to protect your data, often called "envelope encryption" or "wrapping keys".

A Customer Master Key (CMK), sometimes called a Key Management System (KMS) key, is the top-level key you create in your customer provisioned key provider, such as a cloud KMS. The CMK encrypts Data Encryption Keys (DEK), which in turn encrypt the fields in your documents. Without access to a CMK, your client application cannot decrypt the associated DEKs.

MongoDB stores DEKs, encrypted with your CMK, in the Key Vault collection as BSON documents. MongoDB can never decrypt the DEKs, as key management is client-side and customer controlled.

If you delete a DEK, all fields encrypted with that DEK become permanently unreadable. If you delete a CMK, all fields encrypted with a DEK using that CMK become permanently unreadable.

Warning

The Customer Master Key is the most sensitive key in Queryable Encryption. If your CMK is compromised, all of your encrypted data can be decrypted. Use a remote Key Management System to store your CMK.

Important

Use a Remote Key Management Service Provider

Store your Customer Master Key on a remote Key Management System (KMS).

To learn more about why you should use a remote KMS, see Reasons to Use a Remote Key Management System.

To view a list of all supported KMS providers, see the KMS Providers page.

Key Rotation

You rotate your CMK either manually or automatically on your provisioned key provider. MongoDB has no visibility into this process. Once you rotate the CMK, MongoDB uses it to wrap all new DEKs. It does not re-wrap existing encrypted DEKs. These are still wrapped with the prior CMK.

To rotate some or all of the encrypted DEKs in your key vault, use the KeyVault.rewrapManyDataKey() method. It seamlessly re-wraps keys with the new CMK specified, without interrupting your application. The DEKs themselves are left unchanged after re-wrapping them with the new CMK.

For details on rotating keys, see Rotate Encryption Keys.

Key Vault Collections

Your Key Vault collection is the MongoDB collection you use to store encrypted Data Encryption Key (DEK) documents. DEK documents are BSON documents that contain DEKs and have the following structure:

{
  "_id" : UUID(<string>),
  "status" : <int>,
  "masterKey" : {<object>},
  "updateDate" : ISODate(<string>),
  "keyMaterial" : BinData(0,<string>),
  "creationDate" : ISODate(<string>),
  "keyAltNames" : <array>
}

You create your Key Vault collection as you would a standard MongoDB collection. Your Key Vault collection must have a unique index on the keyAltNames field. To check if the unique index exists, run the listIndexes command against the Key Vault collection:

1db.runCommand({
2   listIndexes: "__keyVault",
3});
1{
2   cursor: {
3      id: Long("0"),
4      ns: 'encryption.__keyVault',
5      firstBatch: [
6         { v: 2, key: { _id: 1 }, name: '_id_' }
7         ]
8   },
9   ok: 1,
10}

If the unique index does not exist, your application must create it before performing DEK management.

To learn how to create a MongoDB collection, see Databases and Collections.

Tip

mongosh Feature

The mongosh method KeyVault.createKey() automatically creates a unique index on the keyAltNames field if one does not exist.

To view diagrams detailing how your DEK, CMK, and Key Vault collection interact in all supported KMS provider architectures, see KMS Providers.

Key Vault collection Name

You may use any non-admin namespace to store your Key Vault collection. By convention, the examples throughout this documentation use the encryption.__keyVault namespace.

Warning

Do not use the admin database to store encryption-related collections. If you use the admin database for this collection, your MongoDB client may not be able to access or decrypt your data due to lack of permissions.

Permissions

Applications with read access to the Key Vault collection can retrieve encrypted Data Encryption Key (DEK)s by querying the collection. However, only applications with access to the Customer Master Key (CMK) used to encrypt a DEK can use that DEK for encryption or decryption. You must grant your application access to both the Key Vault collection and your CMK to encrypt and decrypt documents with a DEK.

To learn how to grant access to a MongoDB collection, see Manage Users and Roles in the MongoDB manual.

To learn how to grant your application access to your Customer Master Key, see the Queryable Encryption Automatic Encryption Tutorial or CSFLE Automatic Encryption Tutorial.

Key Vault Cluster

By default, MongoDB stores the Key Vault collection on the connected cluster. MongoDB also supports hosting the Key Vault collection on a different MongoDB deployment than the connected cluster. Applications must have access to both the cluster that hosts your Key Vault collection and the connection cluster to perform Queryable Encryption operations.

To specify the cluster that hosts your Key Vault collection, use the keyVaultClient field of your client's MongoClient object. To learn more about the specific configuration options in your client's MongoClient object, see the MongoClient Options for Queryable Encryption or MongoClient Options for CSFLE.

Update a Key Vault Collection

To add a DEK to your Key Vault collection, use the createKey method of a ClientEncryption object.

To delete or update a DEK, use one of the following mechanisms:

  • The rewrapManyDataKey method

  • Standard CRUD operations

To learn more about the rewrapManyDataKey method, see the documentation of the method for your client or driver:

Tip

mongosh Specific Features

mongosh provides the following additional methods for working with your Key Vault collection:

To view a tutorial that shows how to create a Data Encryption Key, see the Queryable Encryption Quick Start or the CSFLE Quick Start.

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KMS Providers